Device for blow-molding containers

ABSTRACT

The device serves for the blow molding of containers that comprise a thermoplastic material, wherein the device has at least one blowing station with at least one blow mold. The blow mold is formed from at least two blow mold segments that are supported by supports, wherein the blow mold has a base extension. The base extension is arranged in such a way that it is capable of being positioned in the direction of a longitudinal axis of the blow mold, and is supported by a base plate. The base plate connects the base extension to a positioning device. The base plate is additionally connected to the base extension by a profiled coupling section, wherein this profiled coupling section is formed from a coupling element, which is connected to the base plate, along with a counter element that is connected to the base extension. The profiled coupling section is capable of being actuated via a manual lever. At least two hollow coupling plugs are arranged a certain distance from the profiled coupling section, wherein these coupling plugs are capable of being introduced into self-sealing coupling sockets.

[0001] The invention pertains to a device for the blow molding ofcontainers that comprise a thermoplastic material, wherein the devicehas at least one blowing station with at least one blow mold, which isformed from at least two blow mold segments that are supported bysupports, wherein the blow mold has a base extension that is arranged insuch a way that it is capable of being positioned in the direction of alongitudinal axis of the blow mold, and wherein the base extension issupported by a base plate that connects the base extension to apositioning device.

[0002] In the case of such a container molding process affected via theaction of pressure due to blowing, the pre-molded elements comprised ofa thermoplastic material, e.g. pre-molded elements comprised of PET(Poly(ethylene terephthalate)), are forwarded to various processingstations inside a blowing machine. Typically, such a blowing machine hasa heating device as well as a blowing device, whereby the pre-moldedelement, which has been regulated thermostatically beforehand, isexpanded, by means of biaxial orientation, to produce a container in theregion of the blowing device. Expansion takes place with the help ofcompressed air that is introduced into the pre-molded element that is tobe expanded. The technical process in the case of such an expansion ofthe pre-molded element is explained in DE-OS 43 40 291.

[0003] The basic structure of a blowing station for use in moldingcontainers is described in DE-OS 42 12 583. Possibilities forthermostatically regulating the pre-molded elements are explained inDE-OS 23 52 926.

[0004] The pre-molded elements and the blown containers can betransported within the blow-molding device by means of various handlingdevices. The use of transportation mandrels, on which the pre-moldedelements are positioned, has proven especially valuable in practice.However, the pre-molded elements can also be handled by means of othersupporting devices. Available constructions also include the use ofgrappling tongs for handling the pre-molded elements, and the use ofexpansion mandrels, which can be introduced into an opening region ofthe pre-molded element for supporting purposes.

[0005] The handling of the pre-molded elements explained above iseffected, on the one hand, using the so-called two-stage process, inwhich the pre-molded elements are first manufactured in an injectionmolding process, and then are stored on an interim basis; it is onlylater that they are conditioned, in terms of their thermostaticallyregulated temperature, and inflated to produce a container. On the otherhand, use is also made of the so-called one-stage process, in which thepre-molded elements are suitably thermostatically regulated immediatelyfollowing their manufacture, by means of injection molding technology,and adequate solidification, after which they are inflated.

[0006] Various embodiments of blowing stations that are used are known.In the case of blowing stations that are arranged on rotating transportwheels, the ability of the mold supports to be opened on a hinge in abook-like manner is frequently encountered. However, it is also possibleto use mold supports that can be moved relative to one another, or thatare guided in a different manner. In the case of spatially fixed blowingstations, which are especially well suited for housing several cavitiesfor container molding purposes, plates, which are typically arrangedparallel to one another, are used as mold supports.

[0007] In addition to the two blow mold segments, a conventional blowmold comprises a base extension that is capable of being positioned.Such a base extension is required when undercuts occur in a horizontaldirection in the base region of the container that is to bemanufactured. After the container has been molded, the base extension israised, and the two blow mold segments are separated from one another inorder to allow the blown container to be extracted from the blowingstation. The base extension is usually screw-fitted to a base plate. Inaddition, screw connections are provided in order connect cooling waterchannels inside the base extension to suitable supply lines.

[0008] In the event of a product change, it is necessary to change boththe blow mold segments and the base extension in order to generate thecontainer contours for the new product. The corresponding change of thebase extension is relatively labor intensive because of the screwfitting that is provided for the base extension and the base plate,along with the screw fittings for the connections for the coolingmedium.

[0009] The object of the present invention is therefore to construct adevice of the type designated at the beginning, such that changing thebase extension can take place at reduced operational expense.

[0010] In accordance with the invention, this object is attained byconnecting the base plate to the base extension by means of a profiledcoupling section—wherein this profiled coupling section is formed from acoupling element, which is connected to the base plate, along with acounter element, which is connected to the base extension, and whereinthe profiled coupling section is capable of being actuated via a manuallever—and by arranging at least two hollow coupling plugs at a certaindistance from the profiled coupling section, wherein these couplingplugs are capable of being inserted into self-sealing coupling sockets.

[0011] By using the profiled coupling section, which comprises thecoupling element and the counter element, it is possible to create or,respectively, to abolish a mechanical connection between the base plateand the base extension at low operational expense and with very littleconsumption of time. Along with the creation of the coupling connection,the use of the coupling plugs and coupling sockets also creates therequired connections for the supply and draining off of the coolingwater in one operational step.

[0012] The manual lever permits the coupling operation to be actuatedusing very little force. When plugging the coupling element and thecounter element together, the coupling plugs are also simultaneouslyinserted into the associated coupling sockets. The actual arrestment or,respectively, the release from arrestment in the case of the converseoperating sequence, is effected by shifting the manual lever.

[0013] A compact coupling device is provided by designing the couplingelement such that it can expand.

[0014] An especially reliable and low-wear coupling can be provided ifthe coupling element has at least one oblique flank that positions atleast one ball transversely to a longitudinal axis.

[0015] Smoothness of the coupling operation, which assists manualactuation, can also be achieved by forming the coupling element, inessence, from a basic element and a guide that supports the basicelement movably in the direction of the longitudinal axis, and byarranging for the guide to have at least one recess in it, which isoriented obliquely to the longitudinal axis, to allow mounting of atleast one ball.

[0016] In order to ensure the defined allocation of coupling plugs tocoupling sockets, it is proposed that the base plate should have atleast one rotation safeguarding device for positioning definitionrelative to the base extension.

[0017] The rotation safeguarding device can be produced, for example, byconfiguring the rotation safeguarding device in the form of a projectingprofiled section that is capable of being inserted into a profiledcounter-section.

[0018] The provision of a rotation safeguarding device withoutadditional components is possible by forming the rotation safeguardingdevice via an asymmetrical arrangement of the coupling plugs.

[0019] Typical utilization entails configuring the coupling plugs in theform of the components of a water coupling unit.

[0020] In order to ensure freedom from play, it is proposed that atleast one pre-tensioning element be arranged a certain distance from theprofiled coupling section.

[0021] High security against tipping over can be achieved by arrangingat least three pre-tensioning elements a certain distance from theprofiled coupling section.

[0022] Another feature that contributes to ensuring security againsttipping over is that the pre-tensioning elements are arranged at a smalldistance from the periphery of the base plate.

[0023] Examples of embodiments of the invention are illustratedschematically in the drawings. The following aspects are shown.

[0024]FIG. 1: shows a perspective illustration of a blowing station forthe manufacture of containers from pre-molded elements;

[0025]FIG. 2: shows a longitudinal section through a blow mold in whicha pre-molded element is being stretched and expanded;

[0026]FIG. 3: shows a sketch illustrating a basic structure for a devicefor the blow molding of containers;

[0027]FIG. 4: shows a plan view onto a base plate with a manual lever;

[0028]FIG. 5: shows a cross section in accordance with the line V-V inFIG. 4;

[0029]FIG. 6: shows a cross section in accordance with the line VI-VI inFIG. 4;

[0030]FIG. 7: shows a rotated cross section in accordance with thesection line VI-VII in FIG. 4; and

[0031]FIG. 8: shows an enlarged illustration, in schematic form,depicting the engagement of the coupling element with the counterelement.

[0032] The basic structure of a device for the reshaping of pre-moldedelements (1) into containers (13) is illustrated in FIG. 1 and FIG. 2.

[0033] The device for molding the container (13) comprises, in essence,a blowing station (33), which is provided with a blow mold (34), intowhich a pre-molded element (1) is capable of being inserted. Thepre-molded element (1) can be an injection molded component comprisingpoly(ethylene terephthalate). In order to permit the insertion of thepre-molded element (1) into the blow mold (34), and in order to permitthe removal of the finished container, the blow mold (34) comprises blowmold segments (35, 36) and a base extension (37) that is capable ofbeing positioned by a lifting device (38). The pre-molded element (1)can be supported by a transport mandrel (39) in the region of theblowing station (33), wherein the transport mandrel, along with thepre-molded element (1), passes through a plurality of treatment stationsinside the device. However, it is also possible to insert the pre-moldedelement (1) directly into the blow mold (34) by means of e.g. tongs orother handling implements.

[0034] In order to permit the admission of compressed air, a connectingpiston (40) is arranged below the transport mandrel (39), wherein theconnecting piston supplies compressed air to the pre-molded element (1)and simultaneously provides sealing off relative to the transportmandrel (39). In the case of a modified construction, however, it isalso basically conceivable that fixed compressed air supply lines may beused.

[0035] Stretching of the pre-molded element (1) takes place with thehelp of a stretching rod (41) that is positioned by means of a cylinder(42). However, it is also basically conceivable to carry out mechanicalpositioning of the stretching rod (41) by means of curved segments thatare impacted by sensing rollers. The use of curved segments isespecially expedient when a plurality of blowing stations (33) arearranged on a rotating blowing wheel. The use of cylinders (42) isexpedient when blowing stations (33) that are arranged in a spatiallyfixed manner are provided.

[0036] In the case of the form of embodiment that is illustrated in FIG.1, the stretching system is formed in such a way that a tandemarrangement of two cylinders (42) is provided. Prior to the start of theactual stretching process, a primary cylinder (43) initially drives thestretching rod (41) into the region of the base (7) of the pre-moldedelement (1). During the actual stretching process, a secondary cylinder(45) or a curved steering system positions the primary cylinder (43)with the stretching rod, which has been driven out, along with acarriage (44) that supports the primary cylinder (43). In particular,thought has been devoted to making use of the secondary cylinder (45) ina curved steered manner, such that an updated stretching position iscreated by a guide roller (46) that glides along a curved path duringthe implementation of the stretching process. The guide roller (46) ispressed against the guide track by the secondary cylinder (45). Thecarriage (44) glides along two guide elements (47).

[0037] Following the closure of the blow mold segments (35, 36), whichare arranged in the region of the supports (48, 49), locking of thesupports (48) relative to one another takes place with the help of alocking device (50).

[0038] In accordance with FIG. 2, the use of separate screw-threadedinserts (51) is provided in the region of the blow mold (34) in order toundertake adaptation to the different shapes of the opening section (2).

[0039] In addition to the blown container (13), FIG. 2 also shows thepre-molded element (1), which is drawn in dashed lines, together with adeveloping container bubble (14) in schematic form.

[0040]FIG. 3 shows the basic structure of a blowing machine that isprovided with a rotating heating wheel (52) as well as a rotatingblowing wheel (53). Starting from the input unit (54) for theintroduction of the pre-molded elements, the pre-molded elements (1) aretransported into the region of the heating wheel by means of transferwheels (55, 56). Radiant heaters (57) and blowers (58) are arrangedalong the heating wheel (52) in order to thermostatically regulate thepre-molded elements (1). After adequate thermostatic regulation of thepre-molded elements (1), these are transferred to the blowing wheel(53), wherein blowing stations (33) have been arranged in the region ofthis blowing wheel. The finished, blown containers (13) are fed to anoutput section (59) by means of additional transfer wheels.

[0041] In order to be able to re-shape a pre-molded element (1) into acontainer (13) in such a way that the container (13) will have materialproperties that ensure the long usability of foodstuffs, especiallybeverages, that are introduced into the interior of the container (13),specific procedural steps must be adhered to during the heating andorientation of the pre-molded elements (1). In addition, advantageouseffects can be achieved by adhering to specific procedures with regardto dimensions.

[0042] Various synthetic materials can be used as the thermoplasticmaterial, e.g. PET, PEN, or PP.

[0043] The expansion of the pre-molded element (1) during theorientation process takes place by admitting compressed air. Thecompressed air feed is subdivided into a pre-blowing phase, in whichgas, e.g. compressed air, is supplied at a low level of pressure, and asubsequent main blowing phase in which gas is supplied at a higher levelof pressure. Compressed air at a pressure of between 10 bar and 25 baris typically used during the pre-blowing phase, and compressed air at apressure of between 25 bar and 40 bar is fed in during the main blowingphase.

[0044]FIG. 4 shows a plan view onto a base plate (2) with a manual lever(3) that has been provided for connecting the base extension (37) to thelifting device (38). The base plate (2) is equipped with a couplingelement (4) in order to connect the base plate (2) to the base extension(37), wherein this coupling element engages with a counter element (5)on the base extension (37). The coupling element (4) and the counterelement (5) jointly form a profiled coupling section (22).

[0045] In the case of the form of embodiment that is illustrated, thebase extension (37) is provided with hollow coupling plugs (6) thatengage with self-sealing sockets (7) on the base plate (2). The couplingplugs (6) and the sockets (7) serve for supplying a thermostaticregulating medium to the region of the base extension (37), and fordraining it off again. In particular, thought has been devoted to theaspect of arranging the coupling plugs (6) asymmetrically in order toprovide base mold orientation. It is also fundamentally conceivable forthe coupling plugs (6) to be positioned in the region of the base plate(2), and for the sockets (7) to be positioned in the region of the baseextension (37).

[0046]FIG. 4 also shows the arrangement of pre-tensioning elements (8)that ensure freedom from play in the arrested state of the baseextension (7). The pre-tensioning elements (8) can, for example, beconfigured in the form of disk springs, compression springs, or spiralsprings.

[0047] It can be seen from the cross sectional illustration in FIG. 5that, in the case of the embodiment form that is illustrated, thecoupling element (4) has a base element (9) that is provided withoblique flanks (10) in the region of its extension that can beintroduced into the counter element (5). The base element (9) is mountedmovably in a guide (12) in the direction of a longitudinal axis (11),and the oblique flanks (10) act collaboratively with balls (14) that aremounted in obliquely arranged guide recesses (15) in the base element(9). In the event of displacing the base element (9) into the guide(12), the balls (14) are pressed outward transversely to thelongitudinal axis (11) as a result of the collaborative action of theoblique flanks (10), the balls (14), and the guide recesses (15), andthese balls engage from behind with a collar (16) on the counter element(5). As a result, a positive interlocking connection is provided betweenthe base plate (2) and the base extension (37).

[0048] The movement of the base element (9) in the direction of thelongitudinal axis (11) is produced via rotary movement of the manuallever (3), wherein the rotary movement of the manual lever (3) istransferred to the base elements (9) by a redirecting unit (17).

[0049] As an alternative to generating the coupling element (4) by usingthe oblique flanks (10) and the balls (14), it is also possible, forexample, to provide the supporting plate (21) or, as the case may be,the base extension (37) with a connecting column which projects into thebase plate (2) and which is provided with at least one undercut in thedirection of its longitudinal axis. The undercut can, for example, beproduced in the form of a lateral groove or by countersinking. Inaccordance with such an embodiment, the feature is provided whenactuating the manual lever (3) that a locking element is positionedessentially in the horizontal direction and, in the locked state, itengages with the profiled part of the connecting column and leads to apositive interlocking connection between the base plate (2) and thesupporting plate (21) or, as the case may be, the base extension (37).In the case of this embodiment, adequate freedom from play is alsoensured by pre-tensioning elements (8). The arresting element can beconfigured, for example, in the form of a bolt segment. However, boththe shaping of the undercut section of the connecting column and theconfiguration of the arresting element are capable of being varied inmany ways. One merely has to ensure adequate adaptation of therespective shape configurations to one another.

[0050] It can also be seen from FIG. 5 that, in the case of thisembodiment, the pre-tensioning elements (8) are essentially configuredin a bolt-like form, and have spring elements (20) betweencontact-pressure flanks (18, 19), wherein these spring elements arecompressed when linking together the base plate (2) and the baseextension (37). It can also be seen that the base extension (37) has asupporting plate (21) that supports the base mold that is used forproviding the container (13) with its contours, although this base moldis not shown in the illustration depicted.

[0051]FIG. 6 shows the manual lever (3) in fully drawn lines when in thereleasing position, and in dashed lines when in the arresting positionthat corresponds to FIG. 5. It can be seen from FIG. 6 that the baseelement (9) has been pushed out of the guide (12) and that, as a result,the balls (14) have been able to advance sufficiently deeply into theguide recesses (15) that an undercut is no longer present at the collar(16). In this position, it has been possible to remove the baseextension (37) from the base plate (2).

[0052]FIG. 7 shows the collaboration of the contact-pressure flanks (18,19), the pre-tensioning elements (8), and the associated spring elements(20), in the form of an enlarged and rotated illustration.

[0053]FIG. 8 once again illustrates the positioning of the base element(9) relative to the guide (12) in the state in which the base extension(37) can be removed from the base plate (2).

[0054] In order to provide additional safeguarding against tipping over,the pre-tensioning elements (8) are preferably arranged at only a smalldistance from the outer periphery of the base plate (2) or, as the casemay be, the base extension (37). The term small distance is herebyunderstood to mean that the distance of the pre-tensioning elements (8)from the outer periphery of the base plate (2) is less than the distancefrom the profiled coupling section (22). The use of the threepre-tensioning elements (8) that have been depicted in the exemplaryembodiments also contributes to enhanced safeguarding against tippingover.

[0055] As an alternative to the use of separate spring elements (20) inthe case of the pre-tensioning elements (8) that are illustrated in FIG.5, it is also possible to arrange springs in the region of the couplingplug (6) or in the region of the coupling sockets (7), and to utilizethese for building up the pre-tension.

1. Device for the blow molding of containers that comprise athermoplastic material, wherein the device has at least one blowingstation with at least one blow mold, which is formed from at least twoblow mold segments that are supported by supports, wherein the blow moldhas a base extension that is arranged in such a way that it is capableof being positioned in the direction of a longitudinal axis of the blowmold, and wherein the base extension is supported by a base plate thatconnects the base extension to a positioning device, characterized bythe feature that the base plate (2) is connected to the base extension(37) by a profiled coupling section, wherein this profiled couplingsection is formed from a coupling element (4), which is connected to thebase plate (2), along with a counter element (5), which is connected tothe base extension (37), wherein the profiled coupling section iscapable of being actuated via a manual lever (3), and by the fact thatat least two hollow coupling plugs (6) are arranged a certain distancefrom the profiled coupling section (22), wherein these coupling plugsare capable of being inserted into self-sealing coupling sockets (7). 2.Device in accordance with claim 1, characterized in that the couplingelement (4) is formed such that it can be expanded.
 3. Device inaccordance with claim 1 or 2, characterized in that the coupling element(4) has at least one oblique flank (10) that positions at least one ball(14) transversely to a longitudinal axis (11).
 4. Device in accordancewith one of the claims 1 through 3, characterized in that the couplingelement (4) is formed, in essence, from a basic element (9) and a guide(12), which movably supports the basic element (9) in the direction ofthe longitudinal axis (11), and in that the guide (12) has at least onerecess (15) in it, which is oriented obliquely to the longitudinal axis(11), in order to mount at least one ball (14).
 5. Device in accordancewith one of the claims 1 through 4, characterized in that the base plate(12) has at least one rotation-safeguarding device for definingpositioning relative to the base extension (37).
 6. Device in accordancewith claim 5, characterized in that the rotation-safeguarding device isconfigured in the form of a projecting profiled section that is capableof being inserted into a profiled counter-section.
 7. Device inaccordance with claim 5, characterized in that a base mold orientationis created from an asymmetrical arrangement of the coupling plugs (6).8. Device in accordance with one of the claims 1 through 7,characterized in that the coupling plugs (6) are configured in the formof the components of a water coupling unit.
 9. Device in accordance withone of the claims 1 through 8, characterized in that at least onepre-tensioning element (8) is arranged a certain distance from theprofiled coupling section (22).
 10. Device in accordance with claim 9,characterized in that at least three pre-tensioning elements (8) arearranged a certain distance from the profiled coupling section (22). 11.Device in accordance with claim 9 or 10, characterized in that thepre-tensioning elements (8) are arranged a small distance from theperiphery of the base plate (2).